The use of CT has increased rapidly in the past decades. In the U.S. an estimated 11% of diagnostic radiological procedures are currently CTexams, but they contribute an estimated 67% to the collective dose from diagnostic radiology. About 11% of CT exams (about 2.7 million / year in the US) are estimated to be on children under 15. In comparison to adult CT, the combination of higher doses to children for a given exam technique, and the larger lifetime risks per unit dose which apply to children, result in lifetime cancer risks attributable to the radiation exposure from CT which are significantly higher in children than adults. For a given child, the benefits of CT almost always far outweigh the small individual risks, but there is room to reduce the population risk, by reducing pediatric CT exposure settings, and by a somewhat more selective use of pediatric CT. In terms of this population risk, an estimated 2.4 million CT exams / year are given to children in the U.S. and, of these individuats, a preliminary estimate is that about 1,100 will ultimately die from a cancer attributable to the radiation from that exam. It is proposed to use state-of-the art organ dose and risk estimation techniques to produce credible cancer risk estimates associated with pediatric CT, with associated uncertainties, and to present them in an easily accessible form for the radiologist, pediatrician, family physician, and the CT industry communities; this will be done for a wide variety of CT parameters, such as exam type, mAs, kV, filtration, slice thickness, and pitch, for axial and spiral modes, for the spectrum of pediatric body heights and weights. This information will be incorporated into a structured risk communication approach, separating problem appraisal (physicians must first believe the problem is relevant to their patients), and new strategy appraisal (will it work? can I do it? what is the downside?). One central approach within this structure will be a website, in which the material is presented in easily accessible form; both problem appraisal and new strategy appraisal will be the framework. The target audiences will be radiologists, pediatricians, family physicians, and the CT industry. We will use telephone interviews supplemented with survey questions, to aid in web content decisions.